The present disclosure relates to methods of forming semiconductor devices. Semiconductor devices may become more highly integrated to provide high performance and low costs thereof. The integration density of semiconductor devices may be a factor that influences the costs of the semiconductor devices such that high integration degrees of semiconductor devices may be demanded. An integration degree of a conventional two-dimensional (2D) or planar memory device may be mainly determined by an area where a unit memory cell occupies. Therefore, the integration density of the conventional 2D memory device may be affected by the level of a technique of forming fine patterns. However, the use of high-priced equipment to form fine patterns may impede the rate at which the integration density of 2D memory devices continues to increase.
Three-dimensional (3D) semiconductor devices including three-dimensionally arranged memory cells have been proposed to overcome limitations of 2D memory devices. However, production of 3D semiconductor memory devices may be expensive when compared with 2D semiconductor memory devices and may have concerns regarding providing reliable product characteristics.